In recent years, copy machines have been developed which can read a document, such as a color photograph, and generate a high-quality copy in which the colors are accurately reproduced. Such copy machines are now used for a wide variety of applications.
However, the resolution of these copy machines is high enough that someone might think it worthwhile to try to run off multiple copies of bank notes, stock certificates, or other documents which may not be legally reproduced. To prevent such one-touch counterfeiting, it has been suggested (Patent Publication 2-210481) that copy machines should be given the capability of recognizing a characteristic pattern on non-reproducible documents so that copies of such documents will not be output.
FIG. 28 shows the general configuration of a device to provide the capability to prevent copying described above. It consists primarily of image generation unit 50, control unit 51, image formation unit 52 and pattern detection unit 53.
The aforesaid image generation unit 50 consists of an image scanner which reads the document and generates red (R), blue (B) and green (G) image data. Control unit 51 inputs these image data and converts them to yellow (Y), magenta (M), cyan (C) and black (K) image data which can be used in image formation unit 52. Image formation unit 52 accepts the converted image data and transcribes them.
Pattern detection unit 53 determines whether the image data generated by image generation unit 50 contain the characteristic pattern which identifies a non-reproducible document. The result of this determination is output to control unit 51. When control unit 51 receives from unit 53 the result that the characteristic pattern has been found, it outputs a control signal (shown in the drawing by dotted lines) to image formation unit 52 or image generation unit 50 to cease operating. With this method, the generation or output of image data identified by the characteristic pattern will be interrupted, and the copying operation will be halted or the entire surface of the copy which is output will be covered with a particular color.
Recently, printers have been developed which are capable of outputting highly accurate color images. Now anyone with an image scanner, a personal computer and a printer can easily make reproductions of color documents which are as accurate as those of high-resolution copy machines. For this reason a demand has sprung up for a device which could be installed in such a system to prevent the reproduction of specified image data and thereby prevent the system from being used for unlawful copying.